Method and apparatus for compressing a fluid



Oct. 20, 1970 $535,058

' METHOD AND APPARATUS FOR COMPRESSING A FLUID I v'. J. DEVINE Filed .Jan. 2, 1969 M/ Va /V7 02 V/A/E- Vselsaz, U; 05-

I J 1 7 V ATTOP/VEYS United States Patent Oflice 3,535,058 Patented Oct. 20, 1970 3,535,058 METHOD AND APPARATUS FOR COMPRESSING A FLUID Verbol J. Devine, 2912 Epperly Drive, Oklahoma City, Okla. 73115 Filed Jan. 2, 1969, Ser. No. 788,525 Int. Cl. F0411 39/12, 41 6'; F04d 25/16 US. Cl. 418-1 5 Claims ABSTRACT OF THE DISCLOSURE A pair of rotary compressors are connected in series so that the compressed fluid output from the first compressor is directed into the second compressor. In entering the second compressor, a portion of the compressed fluid from the first compressor is bled into a chamber which surrounds the main housing of the second compressor. The chamber is thus filled with a fluid under pressure and this adds strength to the primary structural wall or housing of the second compressor. The compression effect of the second compressor is cumulative with respect to the first compressor so that the output or discharge therefrom is a fluid which has been compressed to a value substantially equivalent to the sum of the capacities of the two compressors operated in series. A suitable cooling device is located between the two compressors to cool the discharge from the first or upstream compressor.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to methods and apparatus for compressing fluids, and more particularly, to a method and apparatus for obtaining a high degree of compression of fluids with a relatively inexpensive portable or mobile apparatus.

BRIEF DESCRIPTION OF THE PRIOR ART It has heretofore beeen proposed to obtain relatively high compression of fluids by providing multiple stages in a single compressor, with such stages being enclosed in a single heavy duty housing and receiving, in sequence, a fluid which is further compressed as it proceeds from one stage to another. Staged compressors of this type have generally been quite expensive, very heavy, and have required thick walled structures in order to contain the gas compressed to a high degree through the several stages of such compressors. Moreover, the bulk and weight of such compressor-s have made it difiicult to transport these compressors from one location to another in a rapid manner, and have made the compressors dilficult to relocate and operate at a different situs without substantial expense and consumption of time.

BRIEF DESCRIPTION OF THE PRESENT INVENTION The present invention provides an improved method and apparatus for achieving high compression of fluids with relatively inexpensive and relatively light weight compressor apparatus. Moreover, the compressor apparatus can be quickly disassembled into a plurality of parts for transport from one location to another and can be quickly reassembled for use at the new location.

Broadly described, the method of the present invention comprises positioning a plurality of rotary compressor units for series flow of a fluid to be compressed from one of the units in consecutive sequence to the other units in the plurality of compressors. -In those compressor units downstream from the first unit traversed by the fluid to be compressed, an outer housing or shell surrounds the main compressor housing or shell and defines therewith an annulus or chamber. A portion of the compressed fluid which is input to each of the downstream compressors is bled into the respective chambers of each of the downstream compressor units as the compressed fluid constituting the input to each of these units enters the respective unit. The fluid under pressure which surrounds the internal or main wall or housing of each of the downstream compressor units thus reinforces or supports this housing, permitting it to be made of less expensive, relatively lightweight material.

Through the use of the series of rotary compressors connected in the manner described, the pres-sure of a fluid may be boosted to a high level with relatively lightweight, inexpensive apparatus. Moreover, the several compressor units employed in the series may be quickly and easily disconnected from each other for transport from one location to another, and may be quickly assembled or set up for use upon arrival at the new situs.

The apparatus utilized in the practice of the method preferably further includes means for cooling the compressed fluid as it flows from an upstream to a downstream compressor unit, thus removing the heat developed in the compressed fluid during each compression step.

From the foregoing description of the invention, it will have become apparent that it is an important object of the present invention to provide relatively lightweight, relatively inexpensive compressor equipment for achieving high compression of fluids.

An additional object of the invention is to provide a high compression apparatus for compressing fluids from substantially atmospheric pressure to a very high pressure which apparatus can be quickly and easily transported from one location to another, and can be assembled and used at each location without difficulty or substantial time delay.

A further object of the invention is to provide a method and apparatus for compressing fluids in an expeditious and eflicient manner.

A further object of the invention is to provide apparatus for achieving high compression of fluids, such apparatus being characterized in a rugged mechanically strong construction which has a long and trouble-free operating life.

Additional objects and advantages of the invention will become apparent from the accompanying drawing which illustrates one embodiment of the invention, when such drawing is considered in conjunction with the detailed description of the invention which follows hereinafter.

,3 BRIEF DESCRIPTION OF THE DRAWING The sole drawing accompanying the application illustrates a relatively simple form of apparatus constituting one embodiment of the invention, such embodiment showing a pair of rotary compressors assembled for the performance of the method of the invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION The method of the invention will be described with reference to the apparatus illustrated in the drawing which depicts one embodiment of the invention which may be utilized in the practice of the method. A pair of Root rotary compressors of a type well known in the art are illustrated, and are designated generally by reference numerals and 12. The rotary compressors 10 and 12 are connected in series by means of a suitable connection 14 interconnecting the discharge 16 from the compressor 10 with the inlet or intake 18 to the compressor 12. Surrounding the fluid flow pathway formed by the discharge 16 and inlet 18 is a suitable thermal control structure designated generally by reference numeral 20. The thermal control structure includes a helically wound cooling coil 22 having an inlet pipe 24 and outlet pipe 25 connected thereto, and surrounded by lagging 26 or other suitable insulation.

For a purpose hereinafter to be described, an outer shell or housing 30 is mounted around the inner or main shell or housing 32 of the compressor 12 and is spaced outwardly therefrom to form a chamber or annulus 34. A small bleed port 36 is provided through the inlet 18 to the compressor 12 to communicate the interior of the inlet with the chamber 34. A suitable check valve structure 38 may be provided in the port 36 for closing this port to prevent flow of a fluid under compression from the chamber 34 into the interior of the inlet 18. It will be noted that the discharge duct 40 from the compressor 12 extends through the outer shell 30. The discharge duct 40 may be connected to the inlet or intake duct of yet another compressor which is added to the series, and it is not desired to limit the present invention to the inclusion of two compressors in series since three, four, or more may also be employed to achieve the primary objective of imparting high pressure to a fluid to be compressed. It will be apparent, of course, that where several of the compressors are connected in series, it will frequently be desirable to include the thermal control structure 20 between each of the compressors to adjust the temperature of the compressed fluid moving in series from one compressor to the other.

In the use of the apparatus depicted in the drawing, a fluid such as air which is to be subjected to compression is introduced to the first rotary compressor 10 through the inlet or intake duct thereto. Let it be assumed that the rating of the compressor 10 is such that the air which passes through this compressor is compressed from atmospheric pressure to a positive pressure of 30 p.s.i.g. The air is, of course, heated in undergoing compression, and it is therefore frequently desirable to cool the compressed air before introducing it to the second rotary compressor 12 where further compression and further heating will occur. Thus, a cooling fluid is circulated through the cooling coils 22 to remove some of the heat from the compressed gas passing from the compressor 10 to the compressor 12.

As the compressed air at 30 p.s.i.g. passes through the intake duct 18 into the second compressor 12, a portion of this air passes through the bleed port 36 by opening the check valve 38. Thus, the chamber 34 surrounding the inner wall or housing 32 of the compressor 12 becomes filled with air under pressure, With such pressure eventually building up to slightly less than the 30 p.s.i.g. value at which it enters the second compressor 12. Thus, inwardly acting pressure is exerted by the compressed air in the chamber 34 against the inner housing or wall 32, and thus this housing is reinforced by this external compressed air and is less likely to rupture or part due to the further compression of air within the compressor. Inside the compressor 12, the air which is input to this unit undergoes further compression. If the compressor 12 is rated for compression of a fluid from atmospheric pressure to 30 p.s.i.g., the result of using the compressor in series with the compressor 10 will be that the air entering the compressor 12 at 30 p.s.i.g. will be further compressed to slightly less than p.s.i.g. Thus, with some expected and tolerable efficiency losses within the compressor 12, a further boost in pressure approximating the sum of the rated capacities of the compressors 10 and 12 can be expected.

The advantage of the method of the present invention is that a method is provided for achieving a high level compression of fluids with relatively inexpensive lightweight and portable equipment. The series connection of the two rotary compressors with the compressed fluid reinforcement of the housing or casing of the downstream compressors to permit higher compression to be achieved therein permits the equipment effecting the high compression to be relatively economically constructed, and to be disassembled into a plurality of relatively lightweight, easily transported elements.

Although a preferred embodiment of the invention has been herein illustrated and described, it will be understood that various other embodiments of the invention can be constructed and various changes can be effected in the method of the invention as herein described without departure from the basic principles of the invention. All such innovations and changes are deemed to be encompassed within the spirit and scope of the invention, and are to be considered as equivalents of the specifically described method and apparatus.

What is claimed is:

1. A method for compressing a fluid comprising:-

connecting a plurality of rotary compressors in series for charging the compressed fluid discharged from upstream compressors to a compressor located downstream therefrom;

charging compressed fluid from each of the upstream compressors to the next adjacent downstream compressor; and simultaneously surrounding the housing of each of said downstream compressors with a portion of the compressed fluid discharged from a compressor upstream therefrom so that fluid pressure is exerted inwardly on said housing.

2. The method defined in claim 1 and further characterized to include the step of cooling compressed fluid flowing between said compressors.

3. A method for compressing a fluid comprising:

forming a chamber around the housing of a first rotary compressor;

connecting said first rotary compressor to a second rotary compressor for receiving the discharge from said second rotary compressor;

connecting said chamber to receive a portion of the discharge from said second rotary compressor; passing a fluid to be compressed through said second rotary compressor to compress said fluid; and passing a portion of the compressed fluid from said second rotary compressor to said first rotary compressor for further compression, and simultaneously, passing a portion of the compressed fluid from said second rotary compressor to said chamber so that said fluid exerts a pressure inwardly on said housing.

4. Apparatus for compresing a fluid comprising:

a first rotary compressor;

at least one additional rotary compressor, said rotary compressors being connected in series for fluid flow from said first rotary compressor to and through said additional rotary compressors in consecutive sequence, said additional rotary compressors each including:

a primary housing;

movable members rotatably mounted in said primary housing for compressing a fluid;

a shell outside of, and spaced from, said primary housing and defining a chamber therewith; and

means adjacent the inlet to said primary housing for admitting to said chamber, a portion of a compressed gas charged to the interior of said housing from the rotary compressor immediately upstream.

5. Apparatus as defined in claim 4 and further characterized to include:

duct means interconnecting the inlet of each of said compressors which is downstream from another one of said compressors with the discharge from said other one of said compressors; and

temperature control means around said duct means.

References Cited UNITED STATES PATENTS 2,837,031 6/1958 Ilune.

2,923,249 2/1960 Lorenz.

3,251,535 5/1966 Wescombe 230-45 X 3,438,570 4/1969 Bobe et a1 230-45 X 3,462,075 8/1969 Dirk et a1 230-238 X DONLEY J. STOCKING, Primary Examiner W. J. KRAUSS, Assistant Examiner US. Cl. X.R. 418-9; 417-243 

